Hello. I was arguing with my friend about Africans having better immune systems than those in developed countries because they are exposed to more viruses while people in developed countries are squeaky clean. She says that our immune systems are the exact same, and that they are not stronger, just better at fighting different diseases native to Africa. I said that it was like a bear-fighter and a programmar fighting sharks. The programmer would not last as long as the bear fighter. What we eventually whittled it down to is this: an American and an African of the same age are moved to a room that contains a disease that neither of them have experienced before. Would the American be more likely to be hurt by the disease than the African?

The human immune system only recognizes epitopes (for B cell and T cell immunity). Each epitopte is a unique protein peptide of varying small size lengths (depending on if it is a B cell or a T cell responding to the epitope).Now epitopes can be similar and can be bound loosely by the immune cell (B or T), but it still has to drag it back to the lymph node and come up with an immune cell that bind to it tightly and begin to attack it aggressively (hopefully before there is too many epitopes in the system to overcome). And then that aggressive immune cell makes a memory cell and that is what I call the immune library for the body.

You are postulating that the African's immune library would be very large compared to the developed world's immune library. This is probably true. But I could also argue that nutrition and what keeps the body in good optimal working order may be lacking in the African (on the whole as a population). Also the African's immune system may have malaria (or any of the diseases that are not 'cured' but can be controlled) in its library, but they can only keep it under control (if given the opportunity of optimal nutrition and medicine).

I also wanted to bring up that there is a theory out there, that says asthma and other acquired autoimmune diseases, may be the outcome of an active immune system that is not given anything to attack, and thus aggressively seeks out an epitope that may be similar (loosely binds to a Self epitope in the maturing of the immune cell but just passes the not Self test and is let loose into the lymph).

It would depend on the mode/mechanism the virus takes, and what genetic makeup the human beings have. It is not a generality that can be answered readily.

So you have leveled the playing field by saying that both the African and the American are optimally healthy. So now I would ask how does this virus enter the body? and what does it do once it is inside.

Now if you are talking about something like the Ebola virus, then they would both be dead, and neither would have a chance. There would be no winner.

Now if we are talking about something like HIV, then we would have to look at the genetics of each. There are people out there who are immune to HIV because they genetically lack the signal protein on the outside of their white blood cells/immune cells (which could be African or American depending on their genetics). - perhaps in this case I would say the African may have a slight advantage as only the survivors with this genetic makeup will be able to procreate, and thus this genetic pool would grow more so in Africa than the Americans.Americans procreate with the virus as we have the availability of medications that keep the virus controlled, while many Africans do not and death does not procreate.A large library would only help if the new virus had an epitope that was similar to another virus that would be remembered by the library. Even though it might not be binding tightly, the immune system still can launch a weak attempt, while it takes the virus back to the lymph centers to process the the virus' epitopes to produce a strong binding and thus a strong attack. This ability to process a strong binding and thus a strong attack would depend on the genetics of the person I think.

Thus, the genetics of processing and maturing immune cells and the mode the virus takes would have to be taken into consideration also.

Overall, I believe they would be equally affected. It would also depend on the people, on whether they had been sick for most of their lives and whether they were stronger or weaker as a result. Some people are incredibly weakened after suffering from an illness, even years after when they are clean. If both people are healthy, it would depend on each person's genetics (whether or not their ancestors had the disease, or had some special advantage) rather than where they come from. I agree with past posts in that an African wouldn't hold an advantage just because of exposure to more diseases, but also that the American wouldn't have any advantage because of past sanitation.

A scientist's job is to find answers without too many holes, or at least come up with interesting ideas with holes that no one will care about.